Bag-type filters are known in the art. Most are provided with a support of some type for the filter bag, e.g., a perforated metal basket. In addition to a bag support, some provision must be made for holding the filter bag in association with the bag support. In general, one can note that a variety of apparatus have been proposed for holding filter media in position within a filter housing. For example, in U.S. Pat. No. 2,081,968 to Wicks et al., a leaf spring acts against the upper portion of a filter cartridge to press the cartridge down into a seat at the bottom of the filter. In Krieck, U.S. Pat. No. 2,106,218, a spiral spring is used to retain a filter cartridge in position. In U.S. Pat. No. 2,156,329 to Beck, a wire frame extending down from the interior of the filter cover holds a filter cartridge in place. U.S. No. Pat. 4,721,563 to Rosaen discloses a filter having a cap portion which threads on to the base portion of a filter. In so doing, a peripheral seal ring extending from the upper peripheral edge of a filter cartridge is captured between the cap and an upper ledge in the base. A centrally located, concentric conduit protruding downward from the cap seals against the upper internal edge of a cylindrical cartridge which is urged upwards by a spring. In U.S. Pat. No. 4,4 19,240 to Rosaen, a filter element and optional liner are held in place by handles pressing against an upper cap. U.S. Pat. Nos. 3,931,015 to Jenkins and 4,253,959 to Tafara describe an apertured flange extending from a generally cylindrically shaped central member depending from a filter cap. The cap is threaded or clamped onto a body portion with the flange pressing against a seal ring for a bag filter. Tafara '959 utilizes plastic construction.
Notwithstanding the above-mentioned patents, it remains an objective in the industry and of the present invention to produce better bag filters more economically and reliably.